Problem after upgrading Ubuntu in EC2


I run Grav on an AWS EC2 with Ubuntu.

I’ve just upgraded the server’s system to Ubuntu 18.

After doing so, when trying to access the website, all that is displayed is:


 * @package    Grav.Core
 * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
 * @license    MIT License; see LICENSE file for details.

namespace Grav;

define('GRAV_PHP_MIN', '5.6.4');

// Ensure vendor libraries exist
$autoload = __DIR__ . '/vendor/autoload.php';
if (!is_file($autoload)) {
    die("Please run: <i>bin/grav install</i>");

if (PHP_SAPI === 'cli-server') {
    if (!isset($_SERVER['PHP_CLI_ROUTER'])) {
       die("PHP webserver requires a router to run Grav, please use: <pre>php -S {$_SERVER['SERVER_NAME']}:{$_SERVER['SERVER_PORT']} system/router.php</pre>");

use Grav\Common\Grav;
use RocketTheme\Toolbox\Event\Event;

if (version_compare($ver = PHP_VERSION, $req = GRAV_PHP_MIN, '<')) {
    die(sprintf('You are running PHP %s, but Grav needs at least <strong>PHP %s</strong> to run.', $ver, $req));

// Register the auto-loader.
$loader = require $autoload;

// Set timezone to default, falls back to system if php.ini not set

// Set internal encoding if mbstring loaded
if (!extension_loaded('mbstring')) {
    die("'mbstring' extension is not loaded.  This is required for Grav to run correctly");

// Get the Grav instance
$grav = Grav::instance(
        'loader' => $loader

// Process the page
try {
} catch (\Exception $e) {
    $grav->fireEvent('onFatalException', new Event(array('exception' => $e)));
    throw $e;

What should I do to fix this?